This invention relates to photocopying machines which incorporate a scanning optical system, and more particularly to drive systems for use in such machines.
Photocopying machines such as those described in U.S. Pat. No. 3,062,109 incorporate a scanning optical system for exposing successive portions of a document to be copied to a moving photosensitive surface. As described in that specification the document may be held stationary during scanning while one or more optical elements (mirror, lenses, lamp, etc.) are driven. Or the optical system may be held stationary during scanning while the document is driven therepast. In the past, scanning systems have been utilized in which the moving element or elements of the scanning system, for example lamps and mirrors, or a document platen, have been mounted on a carriage and this carriage driven in one direction by means of a cable connected to the main drive of the machine through a clutch, and returned to its start-of-scan under the influence of a spring when the clutch is disengaged. In such systems it is most important that the movements of the scanning system and the photosensitive surface be carefully synchronized since loss of synchronization will result in image distortion. Loss of synchronism will result from compliance in the link between the photosensitive surface and the scanning system. This compliance is due at least in part to the mechanical interfaces in the drive and it is an object of this invention to provide a system in which synchronism errors or alleviated.